Investigation of the effect of female larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), and their residues on the production of aggregation pheromone by males

Abstract

The rate of production of aggregation pheromone by male larger grain borer beetles, Prostephanus truncatus (Horn), is greatly reduced in the presence of live, conspecific female beetles. A similar effect is observed in the absence of live female beetles when males are placed on maize that was previously infested with males and females, suggesting that it is due to some chemical residue left by the females. This was shown to persist for at least 15 days, to be involatile and not perceived by receptors on the antennae of the males. Attempts to extract the chemical(s) responsible and transfer it to a new substrate gave variable results. Extraction of previously-infested maize with hexane, ether, dichloromethane, butanone or water under different conditions probably did not remove the suppression effect, but Soxhlet extraction with methanol did. However, when the resulting extract was recoated onto various substrates, no reduction in pheromone production by males could be demonstrated, suggesting that the methanol is extracting and/or destroying the chemical(s) responsible